Storing excess green energy into methane could balance grid

By Tereza Pultarova

Published Friday, January 9, 2015

A proof-of-concept power plant using excess energy from renewable resources to produce methane from biomass will be tested in Sweden.

Developed by engineers from the Karlsruhe Institute of Technology (KIT), the system could help efficiently balance electrical grids strained due to the fluctuation of power production by renewable resources such as wind and solar.

The pilot system, called the DemoSNG unit, is mobile and about the size of a conventional shipping container.

“DemoSNG shows the way to store green power and transport it in our gas grids in the form of methane,” said Thomas Kolb, head of the Engler-Bunte Institute of KIT, who worked on the project.

The researchers believe producing methane from the excess energy has tangible advantages as the infrastructure for methane and gas distribution already exists.

In addition to producing methane from biomass-based carbon dioxide, the surplus energy could also be used to power electrolysis to produce hydrogen.

“The variable operation modes were the biggest challenge during development,” explained Siegfried Bajohr of the Engler-Bunte Institute (EBI) of KIT, the project’s leader.

The DemoSNG unit achieves better results than previous concepts thanks to the use of a nickel-based catalyst contained in metallic honeycomb-like structures, similar to those used in cars to neutralise exhaust gases.

The system produces hydrogen, carbon dioxide and carbon monoxide by gasification of biomass and turns those directly into methane and water.

If further green power excess is left after the completion of the methanation, it can be employed to power electrolysis of the resulting water to produce hydrogen.

“As conventional methanation processes reach their limits at this point, we have developed a new reactor concept,” Bajohr said. ”The DemoSNG plant shows that our concept also works in a large-scale pilot plant.”

The team has completed first tests and is about to ship the unit to Köping in Sweden for integration into gas flows of a biomass gasification plant using wooden residues.

The team said the system’s innovative honeycomb catalyst makes the technology suitable for operations of plants of various sizes including smaller and medium facilities.